Re: [PATCH, powerpc], Fix PR48857, pass/return V2DI as other vector types

[David Edelsohn <dje.gcc@gmail.com>]

On Tue, May 3, 2011 at 5:27 PM, Michael Meissner
<meissner@linux.vnet.ibm.com> wrote:
> When I added VSX support to the powerpc, I overlooked passing and return
> V2DImode arguments, since the only machine operation that supports V2DI is
> vector floating point conversion.  Consequentally, V2DI types were passed and
> returned in GPRs instead of the vector registers on power7.
>
> This patch fixes that so that V2DImode values are passed and returned like
> other vector types.
>
> I did a bootstrap and make check with no regressions, comparing it to a build
> without the patch.  I also wrote a program that passed and returned every
> single type, and I compared the assembly ouptut.  With the exception of
> functions that return or are passed V2DI arguments, the code is identical.  I
> tested:
>
>        -m64                    (implies -mabi=altivec)
>        -m32 -mabi=altivec
>        -m32 -mabi=no-altivec   (no difference here)
>
> Is this patch ok to install?  I will also want to install it in the 4.6 and
> possibly 4.5 trees as well.
>
> [gcc]
> 2011-05-03  Michael Meissner  <meissner@linux.vnet.ibm.com>
>
>        PR target/48857
>        * config/rs6000/rs6000.h (VSX_SCALAR_MODE): Delete.
>        (VSX_MODE): Ditto.
>        (VSX_MOVE_MODE): Ditto.
>        (ALTIVEC_OR_VSX_VECTOR_MODE): New macro, combine all Altivec and
>        VSX vector types.  Add V2DImode.
>        (HARD_REGNO_CALLER_SAVE_MODE): Use it instead of
>        ALTIVEC_VECTOR_MODE and VSX_VECTOR_MODE calls.
>        (MODES_TIEABLE_P): Ditto.
>
>        * config/rs6000/rs6000.c (rs6000_emit_move): Use
>        ALTIVEC_OR_VSX_MODE instead of ALTIVEC_VECTOR_MODE and
>        VSX_VECTOR_MODE.
>        (init_cumulative_args): Ditto.
>        (rs6000_function_arg_boundary): Ditto.
>        (rs6000_function_arg_advance_1): Ditto.
>        (rs6000_function_arg): Ditto.
>        (rs6000_function_ok_for_sibcall): Ditto.
>        (emit_frame_save): Ditto.
>        (rs6000_function_value): Ditto.
>        (rs6000_libcall_value): Ditto.
>
> [gcc/testsuite]
> 2011-05-03  Michael Meissner  <meissner@linux.vnet.ibm.com>
>
>        PR target/48857
>        * gcc.target/powerpc/pr48857.c: New file, make sure V2DI arguments
>        are passed and returned in vector registers.

What does this do to the ABI?  Haven't we now broken the ABI and
broken backwards compatibility?

- David